Multi-slider electrical assemblies including slidable variable resistors or other slidable electrical devices are known and used in graphic equalizers. Such a multi-slider variable resistor or other variable electrical assembly generally comprises a substrate having conductive patterns such as resistor, collector or other elements printed thereon, and a case mounted on the substrate to define the outer margin of the assembly. Guide blocks are interposed between the substrate and the case to define a plurality of parallel slits, a plurality of carriers are received in the slits of the guide blocks and a plurality of sliders are each secured to the bottom surface of the carrier to slide on the conductive patterns when the carrier is moved. Each carrier has a lever extending upward through one of elongated grooves in the case to provide an external knob. When the lever is moved along the elongated groove, the associated slider moves on the conductive patterns to change its position and hence vary the electrical output of the device.
In the prior art multi-slider assembly, the case is a plastic resin molded piece, and the mold must be changed if a different number of grooves is required in the case. This causes an increase in the manufacturing cost of the assembly.
To overcome this drawback, the Applicant proposed an improvement disclosed in Japanese Utility Model Application No. 118838/1985 and shown in FIG. 8 of the present application.
As shown in FIGS. 6-8, a prior art case 8 is formed from a plated hoop-shaped metal sheet which is press-cut to provide a number of elongated grooves 8a and engage projections 8d. The elongated grooves 8a are to projectingly receive levers 4a of carriers 4 therein. After this, the metal sheet is cut along transverse lines (A--A line and B--B line) apart from the elongated grooves 8a. Subsequently, through holes 8b are punched, unnecessary engage projections 8d are removed, and the sheet is bent along lines C--C and D--D to form an upper plate 8f and two side walls 8c. The case 8 having a desired number of grooves as shown in FIG. 7 is obtained. As shown in FIG. 6, the case 8 is fixed to an insulative substrate 1 by bending the engage projections 8d on to the bottom surface of the substrate 1.
In the Applicant's prior proposal, the substrate 1 is made from phenolic or other insulative material which is so fragile that it is often crushed at portions grasped by the engage projections of the case 8.
Further, the metal case 8 operates as an antenna generating external noises in the circuit patterns unless the case 8 is reliably connected to ground.